Among display devices for displaying image information on a screen, a Braun tube display device (or, cathode ray tube(CRT)) has been most popularly used up to date. However, the CRT has several disadvantages that it is bulky and heavy in comparison with its display area.
Accordingly, a thin film type flat panel display device, which can be easily used anywhere because of its slimness, has been developed, and is gradually substituting the Braun tube display device.
The principles of the optical anisotropy and polarization of liquid crystals are employed in driving such a LCD. Because liquid crystal has an elongate structure, it has a direction and a polarizability of a molecule array. The direction of the molecule array can be controlled by artificially applying an electric field to the liquid crystal. When the alignment direction is controlled by such an electric field, a light is transmitted or blocked according to the alignment direction of the liquid crystal molecules due to the optical anisotropy of the liquid crystal, thereby displaying colors and images.
In an active matrix LCD, an active device with a nonlinear characteristic is added into each of pixels arranged in a shape of matrix. Thus, an operation of each pixel is controlled using a switching characteristic of this device.
Meanwhile, in recently, various researches for a dual display have been undertaken, which is capable of displaying an image in both front and rear of LCD.